Neural correlates of executive functions in people with amnestic mild cognitive impairment

Abstract

AbstractBackgroundPeople with amnestic mild cognitive impairment (aMCI) often experience difficulties in cognitive domains other than memory, including executive functioning. Though these deficits are well documented, their neural correlates remain unknown. The aim of this study was to: (1) identify differences in brain activity and connectivity during planning in people with aMCI and cognitively healthy older adults, and (2) find whether planning‐related activity and connectivity are associated with cognitive performance.MethodTwenty‐five people with aMCI (67.6 ± 5.2 y, 6 F, 3 left‐handed) and 15 cognitively healthy older adults (66.4 ± 4.3 y, 5 F, all right‐handed) performed a visuospatial planning task (Tower of London; ToL) during functional magnetic resonance imaging (fMRI). Task‐related brain activation and connectivity were compared between the two groups and regressed against measures of executive functions (Digit Symbol Substitution Test, DSST; Trail Making Test difference score, TMT B‐A) and delayed recall (Rey Auditory Verbal Learning). All fMRI analyses were controlled for scores on the Geriatric Depression Scale, the Apathy Evaluation Scale, the DSST, and the TMT B‐A, and corrected for multiple comparisons at cluster‐level.ResultAs expected, people with aMCI had significantly poorer delayed recall than cognitively healthy older adults (F = 15.8, p < 0.0001). They also scored worse on the DSST (F = 5.5, p = 0.025) and the TMT B‐A (U = 77.5, p = 0.012), and were less accurate on the ToL task (F = 10.7, p = 0.002).During planning, people with aMCI had less activation in two clusters, both located in the precentral gyrus (p = 0.013 and p = 0.047). Across all participants, better performance on the DSST was associated with stronger anti‐correlation between a seed in the left middle frontal gyrus and a cluster in bilateral frontal poles (p = 0.012).ConclusionImpaired planning in people with aMCI appears to be underpinned by less activation in areas associated with sequence planning and visuospatial attention. Interestingly, more negative connectivity between the left middle frontal gyrus and frontal areas involved in working memory and task flexibility was associated with better performance on a task of executive functions.